Metal oxide electrodes as sensors in complexometric titrations

Area of Science:

• Analytical Chemistry
• Electrochemistry

Background:

• Potentiometric titrations are crucial for ion quantification.
• Lead dioxide (PbO(2)) and manganese dioxide (MnO(2)) electrodes have been explored for specific ion analyses.
• Anomalies in titration curves can complicate accurate measurements.

Purpose of the Study:

• To investigate potentiometric titrations of lead and manganese using PbO(2) and MnO(2) electrodes.
• To explain observed anomalies in titration curves.
• To assess the utility of the MnO(2) electrode for titrating other divalent metal ions.

Main Methods:

• Potentiometric monitoring of EDTA titrations.
• Utilizing PbO(2) and MnO(2) electrodes as indicator electrodes.
• Titration of lead (Pb2+), manganese (Mn2+), barium (Ba2+), calcium (Ca2+), cadmium (Cd2+), and copper (Cu2+) ions.

Main Results:

• Anomalies in titration curves were observed and explained.
• Formation of an Mn(III)-EDTA complex with the MnO(2) electrode caused diminished potential breaks.
• Potential electrode coating reactions with the titrant in acidic solutions may explain PbO(2) electrode curve distortions.
• The MnO(2) electrode achieved <1% error for titrating Ba2+, Ca2+, Cd2+, and Cu2+.

Conclusions:

• The MnO(2) electrode is a viable and accurate tool for potentiometric titration of several divalent metal ions.
• Understanding electrode-specific anomalies is key to successful potentiometric analysis.
• EDTA titrations with specialized electrodes offer precise quantification of target ions.